string_linear_equation.rb

# str = "3x + 2 + x/6 = 5", expected: 0.94736
# str = "3x = 9", expected: 3.0
# str = '3x - 2 + x/6 = 5', expected: 2.21
# program to solve linear equation with arg as str format of linear eqn.
def linear_equation(str)
	elements = str.split(' ')
	nums = []
	xs = []
	signs = ['+', "-"]
	next_sign = 1
	n = elements.size
	elements[0..(n-3)].each do |ele|
		if ele.include?('x')
			out = ele[/\d+/].to_f
			out = 1.0/out if ele.include?('/')
			xs << out*next_sign
			next
		end
		if ele.exclude?('+') && ele.exclude?('-')
			nums << ele[/\d+/].to_f*next_sign
			next
		end
		next_sign = case ele
								when "+"
									1
								when "-"
									-1
								end

	end
	a = xs.sum
	b = nums.compact.sum
	c = elements.last.to_i
	return (c-b)/a
end